Method and apparatus for demixing of degenerate mixtures

Abstract

A method and system for blind channel estimation comprises acquiring two mixtures of at least one at least weakly W-disjoint orthogonal source signal, calculating point-by-point ratios of a transform of a time-window of each of said mixture signals, determining channel parameter estimates from said ratios, constructing a histogram of said channel parameter estimates, repeating the calculating, determining and constructing steps for successive time windows of the mixture signals, and selecting as estimates of said channel parameters those estimates associated with identified peaks on said histogram.

What is claimed is:  
     
       1. A method for blind channel estimation, comprising: 
       acquiring two mixtures of at least one at least weakly W-disjoint orthogonal source signal;  
       calculating point-by-point ratios of a transform of a time-window of each of said mixture signals;  
       determining channel parameter estimates from said ratios;  
       constructing a histogram of said channel parameter estimates;  
       repeating the calculating, determining and constructing steps for successive time windows of the mixture signals; and  
       selecting as estimates of said channel parameters those estimates associated with identified peaks on said histogram.  
     
     
       2. The method of  claim 1 , wherein said transform comprises a Fourier transform. 
     
     
       3. The method of  claim 1 , further including estimating the number of source signals from the number of peaks in the histogram. 
     
     
       4. The method of  claim 1 , wherein said channel is an acoustic communications channel. 
     
     
       5. The method of  claim 1 , wherein said acquiring step uses two microphones in a hearing aid. 
     
     
       6. The method of  claim 1 , wherein said channel is an EM wireless communications channel. 
     
     
       7. The method of  claim 1 , wherein said channel parameter is the amplitude. 
     
     
       8. The method of  claim 1 , wherein said channel parameter is the delay. 
     
     
       9. The method of  claim 1 , wherein said channel parameter is the amplitude and delay. 
     
     
       10. The method of  claim 1 , wherein said channel parameter is the direction of arrival. 
     
     
       11. The method of  claim 1 , wherein said channel parameter is the normalized distance to a source signal. 
     
     
       12. The method of  claim 1 , wherein said channel estimates are used for constructing a radiation field map. 
     
     
       13. The method of  claim 10 , wherein said channel estimates are used for constructing a radiation field map. 
     
     
       14. The method of  claim 11 , wherein said channel estimates are used for constructing a radiation field map. 
     
     
       15. The method of  claim 1 , wherein the channel parameter is the number of source signals. 
     
     
       16. The method of  claim 1 , wherein the channel parameter is a reduced attenuation coefficient. 
     
     
       17. The method of  claim 1 , wherein said channel estimates are used for adaptive antenna beamforming. 
     
     
       18. Apparatus for blind channel estimation, comprising: 
       two microphones for acquiring two mixtures of at least one at least weakly W-disjoint orthogonal source signal;  
       transform means for developing a windowed transform for each of said two mixture signals;  
       a divider for determining point-by-point ratios of said windowed transforms;  
       a processor for determining channel parameter estimates from said ratios; constructing a histogram of said channel parameter estimates; repeating the calculating, determining, and constructing steps for successive time windows of the mixture signals; and  
       selecting as estimates of said channel parameters those estimates associated with identified peaks on said histogram.  
     
     
       19. A method for demixing of at least weakly W-disjoint orthogonal mixture signals, comprising the steps of: 
       acquiring one or more channel parameter estimates;  
       calculating point-by-point ratios of a transform of a time-window of each of said mixture signals;  
       assigning the value for each point in the transform of a time-window of one of the mixture signals to a first signal source if the estimated channel parameters determined from the ratio are within a given threshold of one of the acquired channel parameter estimates or, if more than one estimate is provided, to the closest of the acquired channel parameter estimates;  
       repeating the above step for each point in the transform in successive time-windows of the mixture signal;  
       reconstructing time domain signals from the assigned values of signals by inverse transforming an accumulation of the assigned values for each signal.  
     
     
       20. The method of  claim 19 , wherein said mixture signals are anechoic time delay mixture signals. 
     
     
       21. The method of  claim 19 , wherein said mixture signals mixtures contain decorrelated multipath contributions. 
     
     
       22. The method of  claim 19 , wherein said mixture signals contain weak multipath contributions. 
     
     
       23. The method of  claim 19 , wherein said mixture signals are acquired in a wireless communications channel. 
     
     
       24. The method of  claim 19 , wherein said demixing is provided for multi-user detection in a wireless communications system. 
     
     
       25. The method of  claim 19 , wherein said demixing is provided for background noise reduction in a speech recognition device. 
     
     
       26. The method of  claim 19 , wherein said demixing is provided for background noise reduction in a cellular telephone. 
     
     
       27. The method of  claim 19 , wherein said demixing is provided for background noise reduction in a hearing aid. 
     
     
       28. The method of  claim 19 , wherein said demixing is provided for convolutive mixture signals. 
     
     
       29. The method of  claim 28 , wherein said demixing is provided for user interference reduction in a wireless communication system. 
     
     
       30. The method of  claim 28 , wherein said demixing is provided for multi-user detection in a wireless communication system. 
     
     
       31. The method of  claim 28 , wherein said demixing is provided for background noise reduction in a speech recognition device. 
     
     
       32. The method of  claim 28 , wherein said demixing is provided for background noise reduction in a cellular telephone system. 
     
     
       33. The method of  claim 28 , wherein said demixing is provided for background noise reduction in a hearing aid. 
     
     
       34. A method for voice activity detection, comprising the steps of: 
       setting a voice activity detection flag on;  
       estimating the number of sources in a sound field map;  
       demixing the sound source of interest using a weaker assumption on the nature of the signals;  
       detecting absence of power in said sound source of interest; and  
       setting the voice activity detection flag off.  
     
     
       35. The method of  claim 34 , wherein said voice activity detection is used in a hearing aid, and said sound source of interest is speech. 
     
     
       36. A method for critical sound activity detection, comprising the steps of: 
       setting a critical sound activity detector flag off;  
       computing a sound field map;  
       estimating the number of sources in said sound field map;  
       detecting additional sound sources that match one of the critical sounds in their spectral characteristics; and  
       setting critical sound activity flag on.  
     
     
       37. The method of  claim 36 , wherein said critical sound source of interest is voice sound produced for alert in violation of personal safety in a public or private living area. 
     
     
       38. The method of  claim 36 , wherein said critical sound source of interest is sound discharged by firearms or other explosive devices in a public or private living area.